NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Which diameter of the sun in digital photos ?
From: Greg Rudzinski
Date: 2009 Aug 21, 13:25 -0700
From: Greg Rudzinski
Date: 2009 Aug 21, 13:25 -0700
Marcel, Yes I have compared and cross checked DSLR vertical and horizontal terrestrial angles with Sun diameter measurements. I haven't had any problems getting 2 minutes of arc accuracy (precision about 1 MOA) or better using a 50mm lens. I confidently trust the digital camera celestial navigation concept for practical use aboard small craft even in rough weather. On filtering: If the circular polarizing or neutral density filters are hand held in front of the lens so that only the Sun is filtered and not the horizon then you should get some useful images. One other thing to try is the varying of exposure with photo software. The changing diameter of the Sun with over exposure is obvious during this manipulation process. Greg On Aug 21, 12:38�pm, Marcel Tschudinwrote: > Greg, thank you for your suggestions. > > For this exercise I'm using always the same camera having always the > same lenses.The sun's diameter is measured in a photo-program after > removing all colours except green and in some cases even removing all > but blue. I fear to put an other hand-held filter in front since I > have to measure the distance to the horizon which still must be > visible, since the main purpose is to measure the sun's distance to > the horizon. I have so many only faintly visible sun pictures > confirming the obtained scale that I'm fairly confident that the value > corresponds to what the camera 'sees'. > > Have you ever tried with the same lenses to compare the pixels per > degree you obtained for the sun with those of landscape features? > > Marcel --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---